Extension of the samskivert throttle class to allow updating the operation limit, plus a small manual test class

git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5370 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/java/com/threerings/presents/server/PresentsClient.java

@@ -526,7 +526,7 @@ public class PresentsClient
     }
 
     /**
-     * Creates our incoming messaeg throttle.
+     * Creates our incoming message throttle.
      */
     protected Throttle createIncomingMessageThrottle ()
     {

src/java/com/threerings/presents/server/VariableThrottle.java

@@ -0,0 +1,43 @@
+package com.threerings.presents.server;
+
+import com.samskivert.util.Throttle;
+
+/**
+ * Throttle subclass that allows changing the operation limit.
+ */
+public class VariableThrottle extends Throttle
+{
+    /**
+     * Creates a new updateable throttle.
+     */
+    public VariableThrottle (int operations, long period)
+    {
+        super(operations, period);
+    }
+    
+    /**
+     * Updates the number of operations for this throttle to a new maximum, retaining the current
+     * history of operations if the limit is being increased and truncating the oldest operations
+     * if the limit is decreased.
+     * @param operations the new maximum number of operations
+     */
+    public void updateOpLimit (int operations)
+    {
+        long[] ops = new long[operations];
+        if (operations > _ops.length) {
+            // Copy to a larger buffer, leaving zeroes at the beginning
+            int lastOp = _lastOp + operations - _ops.length;
+            System.arraycopy(_ops, 0, ops, 0, _lastOp);
+            System.arraycopy(_ops, _lastOp, ops, lastOp, _ops.length - _lastOp);
+
+        } else if (operations < _ops.length) {
+            // Copy to a smaller buffer, truncating older operations
+            int lastOp = (_lastOp + _ops.length - operations) % _ops.length;
+            int endCount = Math.min(_ops.length - lastOp, operations);
+            System.arraycopy(_ops, lastOp, ops, 0, endCount);
+            System.arraycopy(_ops, 0, ops, endCount, operations - endCount);
+            _lastOp = 0;
+        }
+        _ops = ops;
+    }
+}